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You are in Home >> Exams >> Mitchell Anaesthetic Notes

Thoracic anaesthesia

Created: 3/7/2006
Updated: 10/1/2007

 

Anaesthetic management of bronchopleural fistula

  • Bronchopleural fistula
    • Communication from major bronchus to pleural space
    • Commonly associated with pneumonectomy, trauma, abscess or empyema
    • Relevant complications
      • Pus may contaminate other lung-associated injuries with trauma
  • Surgery
    • Usually semi-elective
    • Resuturing of bronchial stump, muscle flap to stump, drainage of abscess
      • High risk surgery requiring GA and one-lung ventilation
    • If incidental surgery, GA may be avoided, regional preferred
      • Positioning still important to avoid soiling
  • Patient
    • Commonly debilitated, may have coexistent medical problems
    • Respiratory function assessed
      • Clinical, spirometry, ABGs
    • Routine assessment for thoracic surgery
      • Consideration of epidural
  • Decision to proceed
    • Respiratory function optimized
    • Chest drain inserted to avoid tension pneumothorax and drain pleural collection
  • Induction
    • Objectives
      • Maintain oxygenation and ventilation, avoid tension pneumothorax
      • Avoid soiling good lung
    • Protection of lung requires DLT, bronchial lumen to good side
    • Small leak without infection may be manageable with single-lumen ETT
    • Paediatric patients are typically too small for DLT or FOB --> blocker or endobronchial intubation
    • Fistula reduces effectiveness of mask IPPV, so spontaneous ventilation
    • Ideally awake DLT intubation
      • Topical local anaesthetic to airway
      • Position head-up and bad side down
      • Sedation for intubation
    • Alternatively spontaneously ventilating GA with DLT insertion when deep
    • Verification of DLT position with differential ventilation or FOB
  • Maintenance
    • IPPV to healthy lung
    • Lung with fistula may benefit from small VT ventilation or CPAP below critical pressure for fistula or HFJV
  • Emergence
    • Avoid high airway pressures if fistula has been repaired
      • Hand ventilation or SIMV
  • Postoperative
    • Epidural analgesia
    • HDU monitoring post-op
      • High incidence of arrhythmia post-thoracotomy

Outline your approach to tracheal stenosis surgery

  • Surgery
    • Elective, high risk
    • Cervical level: neck incision
    • More distal stenosis: thoracotomy or sternotomy
  • Stenosis
    • Extrinsic compression, e.g. goitre
      • Usually tracheomalacia: soft tracheal stenosis
      • May be easily splinted with ETT
      • Surgery may not involve opening trachea
    • Scarring
      • Usually firm fibrous stenosis
  • Assessment
    • Routine plus
    • History
      • Symptoms of airway compromise: positional dyspnoea, sleeping position
    • Examination
      • Respiratory examination: upper airway sounds
    • Investigations
      • Pulse oximetry, ABG if obvious compromise
      • Spirometry: may be only slightly blunted by significant stenosis
      • Tomography or CT: define anatomy
  • Preoperative
    • Sedative premedication may worsen function as may anxiety
    • Aspiration prophylaxis: H2 blocker
    • Anticholinergic to reduce secretions
  • Monitoring
    • Routine plus
    • Left radial arterial line (compression of innominate artery during surgery)
  • Induction
    • Technique depends on degree of stenosis and airway control
    • Mild, flexible stenosis with little compromise
      • Conventional IV induction
    • Tracheostomy in situ
      • IV induction and armoured tube in tracheostomy
      • Replacement by surgeon with sterile tube
    • Critical stenosis
      • Inhalational induction with potent volatile agent in 100% O2
      • May take 20 min to achieve anaesthesia
      • e.g. sevoflurane in O2 plus BP support if required
  • Intraoperative
    • Rigid bronchoscopy should delineate degree of stenosis
      • Allow decision about method of ventilation
    • Ventilation options
      • Conventional IPPV
        • Armoured ETT or DLT passing stenosis: sterile or non-sterile
        • Reinforced ETT above stenosis, sterile tube across surgical field
      • Jet ventilation using small catheter
      • Cardiopulmonary bypass
      • Deep hypothermic arrest
    • Head is usually in flexion at the end of the surgery, may be sutured chin-to-chest
  • Emergence
    • Aim for extubation to minimize tension on tracheal anastomoses
      • Spontaneous ventilation, suctioning, extubation either deep to minimize coughing or light with adequate narcotics
    • Fibreoptic scope available in case of need for reintubation

Preparation for lung surgery

  • Assessment
    • Associated diease: IHD, PVD, COAD
    • History
      • Exposures (smoking, occupation)
      • Symptoms
        • Bronchopulmonary, extrapulmonary
        • Intrathoracic, extrathoracic
        • Metastatic, non-metastatic
  • Examination
  • Investigation
    • FBE, U&E, enzymes
    • CXR, CT
    • Pulmonary function testing
      • Whole lung: ABG, spirometry, diffusing capacity
      • Single lung: V/Q testing, split function testing
      • Simulation: occlusion of main stem bronchus or pulmonary artery
      • Exercise testing
      • Risk factors for poor outcome
        • PaCO2 >45 mmHg, MBC or FEV1 <50% predicted, RV >50% of VC, raised PVR (>190 dyne.s.cm-5)
      • Requirements for surgery
        • Predicted postop: FEV1 >0.85 l, PAP <40 mmHg, PaCO2 <60 mmHg, PaO2 >45 mmHg
  • Preparation
    • Optimize respiratory function
      • Cease smoking, bronchodilate, treat infection, mobilize sputum, educate for physio
    • Optimize associated diseases
  • Intraoperative
    • Monitoring
      • Tiered approach
        • Routine
          • FiO2, O2 fail, SpO2, gas analysis, NIBP, ECG, airway P, disconnect, nerve stimulator, temperature
        • Sick patient or major procedure
          • Arterial line, gases, spirometry and derived measurements, CVC
        • Sick patient and major procedure
          • PA catheter and derived measurements, SvO2 and derived measurements
  • Lateral position
  • Placement of PA catheter may need to be verified on II (if in
  • deflated lung, CO and SvO2 measures are inaccurate)

One lung ventilation


Physiology 

  • Hypoxic pulmonary vasoconstriction
    • PVR is locally responsive to PO2
    • Reduced shunt fraction in lung which is partially hypoxic
    • Most effective in reducing fall in PaO2 when 30-70% of lung is hypoxic
    • Inhibited by some agents
      • Volatiles inhibit HPV in vitro but not significantly in humans
      • No intravenous anaesthetics inhibit HPV
      • Direct arterial dilators inhibit HPV (SNP, GTN, Ca2+ antagonists, β agonists), though aminophylline and hydralazine may be safe
  • Distribution of blood flow
    • Lateral positioning reduced lung blood flow by 10% of CO
    • Non-ventilation reduces lung blood flow by 50% due to HPV
    • 1 MAC of isoflurane inhibits HPV to 40% reduction in flow
    • The inhibition of HPV by volatiles is difficult to detect in practice
      • No significant difference from TIVA

Position Left Right
Upright or supine 45% 55%
Right lateral 35% 65%
OLV 18% 82%
+1 MAC iso 21% 79%
Left lateral 55% 45%
OLV 77% 23%
+1 MAC iso 73% 27%

Anaesthetic technique

  • Recommendations
    • High FiO2, precludes N2O use
    • Potent volatile or propofol reduces airway reactivity
    • Narcotic analgesia or thoracic epidural diminishes hypnotic requirement
  • Intubation
    • Response blunted with adequate anaesthesia, narcotic and lignocaine
    • Indications for DLT
      • Absolute
        • Lung isolation for bronchopleural fistula, bullous disease, bleeding, infection, bronchopulmonary lavage
        • Conducting airway surgery or trauma
        • VATS
      • Relative
        • Surgical exposure: aortic, lung, mediastinal, oesophageal, vertebral surgery
        • Differential lung ventilation following unilateral massive PE thrombectomy or with unilateral lung disease
    • DLT insertion
      • Types
        • Carlens left with hook
        • Robertshaw left or right
          • 26, 28, 35, 37, 39 or 41 Fr (4.0 to 6.5 mm lumen diameter)
      • Left side most commonly used unless proximal left main lesion
      • Protocol
        • Check cuffs and connections
        • Conventional laryngoscopy
        • Tip passed with curvature concave-forward
        • Rotated if hook present so hook passes anteriorly through larynx
        • Rotated so tip points to side to be endobronchially intubated and head turned to opposite side
        • Advanced until resistance is met (typically at 29 cm + 1 cm per 10 cm height over 170 cm)
        • Tracheal cuff inflated and bilateral lung ventilation verified
          • If unilateral, may be in too far, withdraw until bilateral
        • Bronchial cuff inflated, bronchial lumen ventilated
          • If bilateral lung inflation ± leak from tracheal lumen, tube is not advanced far enough
          • If lower lobe inflation only, tube is advanced too far
          • If right lung isolation, tube is in right bronchus
          • Verify lung isolation
        • Tracheal lumen ventilated
          • If no apparent ventilation, tube may be too far advanced in either bronchus or entirely in the trachea so deflate bronchial cuff and ventilate to determine position
          • Verify lung isolation
        • Verify position with tracheal lumen fibreoptic bronchoscopy, particularly with right-sided tubes to verify upper lobe bronchus position relative to cuff
        • Verify isolation again after patient positioning
      • Other methods to verify position
        • X-ray, differential capnography or flow-volume loops, surgical palpation
        • Underwater bubble test to verify total lung isolation
    • Other lung isolation techniques
      • Univent, bronchial blockers
      • Place with FOB assistance
  • Ventilation
    • Principles
      • Maintain two-lung ventilation as long as possible
      • High FiO2
      • Initial OLV VT of 10 ml/kg
      • Titrate ventilation to normal PaCO2
    • Strategy to maximize HPV in non-ventilated lung
      • Avoid vasodilation in non-ventilated lung due to
        • Systemic vasodilators, increased PA pressure, increased PvO2 , decreased PCO2
      • Avoid vasoconstriction in ventilated lung due to
        • Hypoxia, decreased PA pressure, increased PCO2, high PEEP
    • Managing falling PaO2
      • Low PEEP to ventilated lung
      • CPAP with 100% O2 to non-ventilated lung
      • Intermittent two-lung ventilation
      • Early PA clamping if lung resection
    • Other options
      • HFPPV, HFJV
        • Lower mean airway pressures
        • Less movement
      • Low flow apnoeic ventilation
        • Theoretically feasible for up to 20 minutes
        • High PaCO2 and severe respiratory acidosis


 

Mediastinoscopy

  • Surgery
    • Suprasternal notch incision
    • Blunt dissection anterior to trachea, posterior to aortic arch down to carina
  • Intraoperative
    • Monitoring
      • Routine, plus
      • Right radial arterial line (for great vessel compression) and left NIBP
      • Large bore IV access in arm and leg (in case of SVC disruption)
    • Induction
      • Conventional relaxant GA (reduced risk of air embolus)
      • Reinforced ETT
    • Maintenance
      • Extreme vigilance required
      • Head-up position reduces bleeding but increases risk of air embolus
      • Complications
        • Massive haemorrhage requiring sternotomy
          • Have rapid infusion device available and blood crossmatched
          • Venous disruption may cause air embolus and require lower limb access for drug administration
        • Pneumothorax
          • Common postoperatively, usually small
        • Recurrent laryngeal nerve injury
          • 50% permanent
        • Compression of aortic arch branches
          • Especially right innominate: cerebral ischaemia
          • Detect with right arm arterial line or pulse oximeter
        • Autonomic reflexes
          • Especially bradycardia, hypotension
  • Postoperative
    • CXR to detect pneumothorax
    • Repeat mediastinoscopy is usually impossible due to scarring

Tracheal resection


Preoperative

  • Preoperative considerations
    • Uncommon major surgery with a shared airway
    • Often poses significant difficulty in maintaining ventilation while allowing surgical access: initially due to disease, then surgical disruption, then fragile reconstructed airway with awkward positioning
    • Requires excellent communication between surgeon and anaesthetist
  • Physical findings
    • Degree of obstruction
    • Ability to lie supine
    • Careful evaluation of airway
    • Ability to cough and clear secretions
    • Respiratory examination
  • Workup
    • Usual assessment of comorbidities (often smokers with coronary disease)
    • Delineation of lesion: X-ray, tomography, fluoroscopy, CT, MRI
    • Imaging of adjacent structures: barium swallow, angiography
    • Respiratory function testing: characteristic flow-volume loop
    • Bronchoscopy, biopsy
    • Not all lesions are resectable: palliation with dilatation, stent or laser
    • Detailed plan for airway management must be discussed and agreed with the surgeon
  • Choice of anaesthesia
    • General anaesthesia
    • Airway management plan agreed before surgery: IPPV, HFPPV, jet or spontaneous ventilation or cardiopulmonary bypass or a combination thereof
    • Epidural placement for postoperative analgesia if a thoracotomy is planned

Intraoperative

  • Monitors/line placement
    • Preoperative sedation used with great caution or not at all in incipient obstruction
    • Large IVs, routine monitors: ECG, SpO2, gas analysis
    • Arterial line indicated (on left for right thoracotomy)
    • Central line or PA catheter only if cardiac disease demands it
    • Sterile circuit and selection of ET tubes at hand including small diameters, armored, and extra-long tubes
    • High frequency positive pressure (or jet) ventilator and second anaesthesia machine available if their use is being considered
    • Cardiopulmonary bypass machine primed and ready if its possible use is planned
  • Intraoperative concerns
    • Possibility of obstruction on induction: have assistance and surgeon present with rigid bronchoscopes available
    • Slow inhalational induction probably safest, alternatively awake fiberoptic-guided intubation after topical anaesthesia to the airway if rigid bronchoscopy is not planned
    • Maintenance with intravenous anesthetic agents allows use of 100% oxygen
  • Intraoperative therapies
    • Ventilation strategies during tracheal resection include:
      • Jet ventilator catheter passed through ETT (which is above resection) for manual or high-frequency jet ventilation 
      • IPPV through sterile ETT inserted by surgeon into trachea below resection (intermittent extubation while sewing anastomosis)
      • For low lesions, bronchial intubation by the surgeon and IPPV to one lung or both separately
      • Spontaneous ventilation (complicated by hypercarbia, coughing and possible airway soiling)
      • Cardiopulmonary bypass (complications of systemic anticoagulation)
    • After anastomosis, airway pressures must be minimized: spontaneous ventilation or low tidal volume IPPV
    • Aim for extubation at end of surgery to minimize exposure of anastomosis to positive airway pressure
    • Reintubation will be difficult (head flexed, oedematous airway) and will require a fiberoptic scope both for intubation and to verify the tube tip is not touching the anastomosis

Postoperative 

  • Postoperative pain
    • Carefully titrated narcotics or epidural infusion
  • Complications
    • Anastomotic dehiscence is associated with poor outcome
    • Greater risk of dehiscence with post-op ventilation, steroids, infection, extensive tracheal disease
    • Reduced risk of dehiscence with use of vascularized flap covering anastomosis
    • Minimize tracheal tension with head flexion (maintained postoperatively with a suture from chin to anterior chest for several days)
    • Head flexion may cause cervical spinal cord compression

Surgical procedure

  • Indications
    • Uncommon surgery for tumor, fistula, stenosis or trauma
    • Tumour must not be invading mediastinum
    • Likely postoperative ventilation is a relative contraindication
  • Procedure
    • Cervial/sternotomy approach to high lesions. Initially head extended and roll between scapulae. Repositioning required for anastomosis with head flexed and roll deflated or removed
    • Right thoracotomy, head flexed approach to low or carinal lesions
  • Surgical concerns
    • Tracheal mobilization to allow anastomosis without tension
    • Maintaining tracheal blood supply
  • Typical EBL
    • Highly variable

Ref: Pisonneault et al. Can J Anaesth 1999; 46: 439-55


Kindly provided by Dr James Mitchell from his pharmacodynamics series


ArticleDate:20060703
SiteSection: Article
 
   
    
                                            
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